Pretty sure it was meant to be a french name. Sure, "triste" does mean "sad" in spanish, but if you take her whole name Triste Savoir, it means "sad knowledge" in french. So, pretty sure he was thinking of a french name rather than a spanish one.

I feel you've misunderstood. The King has plans that conflict with Pinkie's nature and therefore they are at a stalemate. Pinkie takes over when things are getting too dark for her tastes and Sombra can't make any progress because of it. Even to the point that Sombra's own mode of thinking is being tainted by Pinkie (aka he is starting to act more like her). In the beginning he was a violent grump and now in the current update he's still evil but being more sympathetic and kind.

Pinkie is win beating Sombra in her own way but Sombra still controls the body.